This invention relates to energy management systems and more particularly relates to devices and methods for automatically controlling the heating, cooling, ventilation, lighting and other devices in a building to provide a maximum saving of energy. The system is particularly suitable for automatic energy management for a school, office building or a home in which various rooms have a somewhat known occupancy schedule or pattern throughout the year.
A large amount of energy is consumed in the operations of heating, cooling, ventilation, lighting and other loads in a building. Commonly, the heating and cooling operations are controlled automatically with a thermostat or a plurality of thermostates are provided, which initiate these operations according to pre-set temperature limits. The thermostat is located at predetermined central location or the plurality of thermostats are located at predetermined locations in the building. During winter months, the thermostat, set in the heating mode, would commence the operation of the heating equipment when it detects that the ambient temperature in the building has fallen below a pre-set lower temperature limit; and it would turn off the heating equipment when the ambient temperature in the building has reached a pre-set upper temperature limit. In the summer months, the thermostat, set in the cooling mode, would initiate the operation of the cooling equipment when the room ambient temperature has risen above a pre-set upper temperature limit, and it would terminate the operation of the cooling equipment when the ambient temperature has been cooled to a pre-set lower temperature limit. The thermostat would initiate the selected operations regardless of whether or not the building is occupied. Since many buildings may be unoccupied for certain periods of time, the continued operation of the heating or cooling equipment during such unoccupied periods would result in the wastage of a large amount of energy. Attempts have been made to reduce the energy wastage by incorporating a timer in the thermostat in which the timer would additionally terminate the heating or cooling operation set back to an energy saving mode according to certain predetermined time periods of the day at a lower pre-set heating temperature limit or higher pre-set cooling temperature limit when the building is expected to be unoccupied. Such provision is practical only if a building has a regular occupancy schedule, for example, a home in which the residents are normally away at work during the day time, so that the heating and cooling operations may be set back to the energy saving mode. However, such provision may not be used in a school building, office building or in a home in which the occupancy of various rooms may not be regular. This drawback is somewhat alleviated by some known control devices incorporating a sensor to detect the occupancy of the building so as to intercept the heating and cooling operations. Such control devices commonly are provided with programming devices such as a touch panel with which the user would set various functions and operating programs for the heating, ventilation and air conditioning devices. It has been found that most users do not understand how to pre-set such operating programs, resulting in the improper setting or no setting at all of the operating programs and unnecessary wastage of energy.